Vulnerability Database

In the Linux kernel, the following vulnerability has been resolved:

kprobes: Fix possible use-after-free issue on kprobe registration

When unloading a module, its state is changing MODULE_STATE_LIVE -> MODULE_STATE_GOING -> MODULE_STATE_UNFORMED. Each change will take a time. is_module_text_address() and __module_text_address() works with MODULE_STATE_LIVE and MODULE_STATE_GOING. If we use is_module_text_address() and __module_text_address() separately, there is a chance that the first one is succeeded but the next one is failed because module->state becomes MODULE_STATE_UNFORMED between those operations.

In check_kprobe_address_safe(), if the second __module_text_address() is failed, that is ignored because it expected a kernel_text address. But it may have failed simply because module->state has been changed to MODULE_STATE_UNFORMED. In this case, arm_kprobe() will try to modify non-exist module text address (use-after-free).

To fix this problem, we should not use separated is_module_text_address() and __module_text_address(), but use only __module_text_address() once and do try_module_get(module) which is only available with MODULE_STATE_LIVE.